The present invention relates to sealant compositions comprising diutan, and more particularly, the present invention relates to sealant compositions comprising diutan and methods for using such sealant compositions in subterranean operations to form a seal in a subterranean formation.
The production of water with hydrocarbons from subterranean formations can present a major problem and expense in the production of the hydrocarbons. While hydrocarbon-producing wells are usually completed in hydrocarbon-bearing formations, such formations may contain, or may be adjacent to, water-bearing portions. The term “water-bearing portion” is defined herein to include any portion of a subterranean formation that may produce water, including a hydrocarbon-bearing portion that has sufficiently high water saturation such that water may be produced along with hydrocarbons. Although efforts generally are made to locate and avoid such water-bearing portions in drilling subterranean well bores, a well bore may penetrate a water-bearing portion of the formation accidentally (e.g., where a water-bearing portion was not detected prior to drilling the well bore). Moreover, the high mobility of the water may allow it to flow into the well bore by way of natural fractures and/or high permeability streaks present in the formation. Over the life of such wells, the ratio of water to hydrocarbons recovered may be undesirable in view of the cost of producing the water, separating it from the hydrocarbons, and disposing of it, which can represent a significant economic loss.
A variety of techniques have been used to reduce the production of undesired water. Generally, these techniques involve the placement of a material in a well bore penetrating a water-bearing portion of a subterranean formation that may prevent or control the flow of water into the well bore. These materials are referred to herein as “conformance materials.” The techniques used to place these conformance materials are referred to herein as “conformance techniques” or “conformance treatments.” Some techniques involve the injection of particulates, foams, gels, sealants, or blocking polymers into the subterranean formation so as to plug off the water-bearing portions. For example, squeeze cementing techniques may be used wherein a cement slurry is forced with pressure into a void or channel through which water would otherwise flow into the well bore, and the cement is allowed to set and seal off that channel. In other techniques, polymers referred to as “relative permeability modifiers” recently have been used, in some instances, to decrease the production of water with hydrocarbons.